Political pundits identify several fault lines when attempting to describe the political and cultural divisions in America today based on sex, race, age, political ideology, geography, and more. But another fault line has emerged between those who feel an instinctive love of country and those whose feelings toward their county depend on which way the political winds are blowing. This patriotism gap is getting far less attention than it deserves.

A recent Gallup poll finds that 67 percent of Democrats are “extremely” or “very proud” to be Americans, down 11 percentage points since just last year, and a new low since Gallup began measuring such attitudes in 2001.

Based on the decline among Democrats, three out of four U.S. adults now say they are proud to be American, which is also a new low. In the early 2000s, for instance, the share of Americans who said they were proud to be Americans was in the 90s.

Also, the 14 percent of Democrats who say they are either “only a little proud” (9 percent) or “not at all proud” (5 percent) to be American is more than double last year’s number of 6 percent.

Republicans, meanwhile, are just as patriotic as they’ve always been. “Republicans’ pride remains high at 92%,” Gallup reports, “close to the average 94% Gallup has measured for the group since 2001.”

All told, a 25-point gap in patriotic feelings exists between Republicans and Democrats, which, again, is the highest in Gallup’s records.

Americans are a patriotic people. Visiting foreigners sometimes marvel that the Star-Spangled Banner is ubiquitous, not just on the Fourth of July but in front yards and on T-shirts across the country all year round.

But patriotism among liberals has been waning for years, and, as the Gallup poll shows, has now dropped to a new low.

It’s no coincidence that the decline of patriotism on the left has happened at the same time as a similar drop in trust in what used to be the bedrock institutions of American society -- police, military, and the church.

Americans are passionate about our politics, but liberals are on average much more willing to allow politics to determine how they feel about their country. Consider that Barack Obama’s 2008 election victory did not cause a large share of Republicans to feel less patriotic. In fact, the share that felt patriotic stayed the same throughout most of Obama’s 8 years in office.

The left’s patriotism fluctuates much more wildly. Ninety-three percent were very or extremely patriotic immediately after 9/11; just 67 percent are today. 

Considering these numbers, it seems safe to conclude that conservatives’ love of country is unconditional while liberals’ is conditioned on their political and policy preferences.

Their patriotism, in other words, is more fickle than that of conservatives.

Don’t get me wrong: most Democrats are patriotic. The young men and women who join the U.S. military come from both Democratic and Republican households. But what should concern us all are the obvious trends emerging on the left.

So what’s happened over the last year to compel so many liberals to fall out of love with their country? Barack Obama has left office after a lackluster eight years and Donald Trump has become president.

While Trump’s victory gave millions of Americans hope, it also caused many on the left to lose faith. In one pre-election poll, 28 percent of Americans said that they had at least considered leaving the U.S. for good “for a country such as Canada” if Trump were elected. Fourteen percent rated the probability as “very high.” Doing the math, that comes to nearly 50 million Americans. According to the New York Times, immediately following his election victory, “move to Canada” became one of the top trending Google search topics.

It’s sad that a candidate who pledged to "Make America Great Again" has prompted so many liberals to lose faith in their country. It’s also sad that a president’s pledge to put America first on issues such as immigration, trade, and foreign policy would prompt so many to want to abandon their country.

Trump’s election and presidency has brought to the surface the worst instincts of many on the left -- chief among them their ambivalence for the land of the free and the home of the brave.  

The left is preoccupied with what’s wrong with America, from its original sin of slavery to today’s challenges with income inequality. Gallup notes that much of the decline in patriotism has occurred among young people. Having grown up on a steady diet of liberal media, liberal popular culture, and liberal education, many of them see nothing but oppression in their country.

Conservatives also acknowledge America’s sins, both the historical, such as slavery, and those that continue today, such as abortion. But they generally believe that, in spite of its flaws, America is, as Reagan put it “the last best hope of mankind.”

In the end, it’s a much more hopeful vision of America.